The present invention relates to method and apparatus for controlling the operating temperatures within a glass forehearth, and in particular to a versatile, cost-efficient computer control system therefor.
The control system of the present invention is designed to be utilized in a forehearth for thermally conditioning molten glass received from a glass melting furnace, to be fed to a glassware forming machine. Such forehearths typically include an elongated refractory channel which is divided into a series of sections or zones, and are designed to bring the glass to a reduced temperature level and to achieve approximate thermal homogeneity, thereby providing a suitable viscosity for the forming process. These forehearths incorporate a plurality of burners, electrodes, or other heat input means spaced along their sides to replace heat lost to the refractory channel walls, and may in addition include one or more conduits for cooling air to selectively remove heat from portions of the molten glass.
A variety of electronic control systems have been devised for glass forehearth temperature control. Such systems typically include one or a plurality of temperature sensors, for measuring atmospheric temperatures or subsurface temperatures of the molten glass, together with a regulator for controlling the action of the heating (and possibly cooling) devices associated with the forehearth in response to sensor feedback and operator input. Where such forehearth control systems include a plurality of transducer-regulator subsystems, each associated with an individual section or zone of the forehearth, these systems have provided greater precision of control at considerable additional expense. There is a practical need for an improved control system which enjoys the advantages of versatile, precise control of forehearth temperatures over a plurality of zones, with greater economy of design.
Accordingly, it is a paramount object of the invention to achieve improved electronic control systems for temperature control in a glass conditioning forehearth. Such systems should provide precise, efficient thermal control over a plurality of forehearth zones.
A related object is to simplify the electronic hardware design of such control systems, thereby yielding cost savings and other advantages.
Still another object of the invention is to achieve rapid, efficient response to disruptive thermal conditions within the forehearth.